CN115097558B - 2-level inclined grating based on high refractive index material and application thereof - Google Patents
2-level inclined grating based on high refractive index material and application thereof Download PDFInfo
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- CN115097558B CN115097558B CN202210709648.0A CN202210709648A CN115097558B CN 115097558 B CN115097558 B CN 115097558B CN 202210709648 A CN202210709648 A CN 202210709648A CN 115097558 B CN115097558 B CN 115097558B
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- 239000000463 material Substances 0.000 title claims abstract description 23
- 230000003287 optical effect Effects 0.000 claims abstract description 21
- 239000011347 resin Substances 0.000 claims abstract description 7
- 229920005989 resin Polymers 0.000 claims abstract description 7
- 238000000034 method Methods 0.000 claims description 9
- 238000005530 etching Methods 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000013461 design Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 102100029469 WD repeat and HMG-box DNA-binding protein 1 Human genes 0.000 description 1
- 101710097421 WD repeat and HMG-box DNA-binding protein 1 Proteins 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000003190 augmentative effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000004590 computer program Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012634 optical imaging Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000002922 simulated annealing Methods 0.000 description 1
Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/18—Diffraction gratings
- G02B5/1814—Diffraction gratings structurally combined with one or more further optical elements, e.g. lenses, mirrors, prisms or other diffraction gratings
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/0101—Head-up displays characterised by optical features
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/18—Diffraction gratings
- G02B5/1842—Gratings for image generation
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
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- Optics & Photonics (AREA)
- Diffracting Gratings Or Hologram Optical Elements (AREA)
Abstract
The invention discloses a-2-level inclined grating based on a high-refractive-index material, which comprises an optical waveguide layer and a grating layer, wherein the optical waveguide layer and the grating layer are made of a resin material with a refractive index of 1.71, and the grating layer is arranged in an inclined manner. The grating period of the inclined grating is 980-992 nanometers, the duty ratio is 0.74-0.76, the grating depth is 1475-1490 nanometers, and the inclination angle is 26-27 degrees. When TE polarized light is vertically incident, the diffraction efficiency of the 620 nm-2 level of the center wavelength can be higher than 80%. The invention also discloses application of the-2-level inclined grating based on the high-refractive-index material to near-eye display equipment, which is applicable to AR and VR near-eye display equipment, convenient in material acquisition and simple in processing, and has important practical prospect.
Description
Technical Field
The invention relates to the technical field, in particular to a-2-level inclined grating based on a high refractive index material and application thereof.
Background
VR/AR technology has great application prospects and development trends in entertainment, education, medical treatment, military and the like. Near-eye display systems of Augmented Reality (AR) and Virtual Reality (VR) are a key ring, near-eye display devices are devices in which pixels on a display are projected into the human eye by forming a remote virtual image through a series of optical imaging elements, and diffraction gratings are key components in VR/AR near-eye display devices. Common one-dimensional gratings include rectangular gratings, blazed gratings and inclined gratings, with 0-order diffraction of rectangular gratings occupying most of the efficiency and useful diffraction orders being less efficient. Blazed gratings and inclined gratings can be used to improve the performance of diffraction grating waveguides, but when blazed gratings are used in the visible light band, the requirements on the precision of the production process are very high, resulting in low mass production yields. The diffraction energy of a tilted grating can be mostly concentrated in the non-0 order, and is more suitable for waveguide diffraction transmission and imaging, and the application range of the tilted grating is wider than that of a blazed grating, so that the tilted grating has significant advantages in an AR/VR display system based on light guide.
The research design and application of tilted gratings has received much attention. Li Shu et al designed a high efficiency tilted grating [ Prior Art 1: application number 201310285669.5 and prior art 2: application number 201310645651.1), but the inclined grating uses the-1 order diffraction light, and the design wavelength is not suitable for the application in the AR/VR field. In order to improve diffraction efficiency, the conventional scalar grating has not met the requirement, and the design of the high-density inclined grating must adopt maxwell's equations in vector form and combine boundary conditions, and the result is accurately calculated through a coded computer program. Moharam et al have given a strict coupled wave algorithm [ prior art 3:M.G Moharam et al, j. Opt. Soc. Am. A.12, 1077 (1995) ] that can solve the diffraction problem of such high density gratings. And (3) optimizing and designing the inclined grating by utilizing a strict coupled wave analysis and simulated annealing algorithm. To our knowledge, however, no one has so far given the fabrication of-2-order tilted gratings based on high refractive index materials for red light of the commonly used 620nm wavelength.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a-2-order inclined grating based on a high refractive index material, which can realize that the diffraction efficiency of the-2-order with the center wavelength of 620 nanometers is higher than 80 percent when TE polarized light is vertically incident, and the-2-order diffraction order realizes total internal reflection in an optical waveguide layer. Has important practical value in the technical field of AR/VR.
Another technical object of the present invention is to provide an application of a-2-level oblique grating based on a high refractive index material to a near-eye display device.
The technical scheme of the invention is as follows: the-2-level inclined grating based on the high-refractive-index material comprises an optical waveguide layer and a grating layer, wherein the optical waveguide layer and the grating layer are made of resin materials with refractive indexes of 1.71, and the grating layer is arranged in an inclined mode.
Further, the grating period of the inclined grating is 980-992 nanometers, the duty ratio is 0.74-0.76, the grating depth is 1475-1490 nanometers, and the inclination angle is 26-27 degrees.
Further, the tilted grating has a grating period of 986 nm, a duty cycle of 0.75, a grating depth of 1482 nm, and a tilt angle of 26.5 °.
The other technical scheme of the invention is as follows: use of a-2-order tilted grating based on a high refractive index material in a near-eye display device.
Compared with the prior art, the invention has the following beneficial effects:
when TE polarized light is vertically incident, the diffraction efficiency of the 620 nm-2 order of the center wavelength can be higher than 80%, and the total internal reflection is realized in the optical waveguide layer. By using the direct writing process and the etching process, the inclined grating suitable for the AR/VR technology can be obtained, and the method has important practical prospect. The invention has the advantages of flexible and convenient use, higher diffraction efficiency and the like, and is an ideal diffraction optical element.
Drawings
Fig. 1 is a schematic diagram of the structure of the tilted grating of the present invention.
Fig. 2 is a schematic diagram of diffraction order propagation after TE incident light is perpendicularly incident.
FIG. 3 is an efficiency plot of diffraction efficiency of the-2 nd order as a function of angle of incidence.
Detailed Description
The present invention will be described in further detail with reference to examples, but embodiments of the present invention are not limited thereto.
Examples
As shown in fig. 1, the present embodiment provides a-2-order oblique grating based on a high refractive index material, including a grating layer 1 and an optical waveguide layer 2.
The optical waveguide layer and the grating layer are made of high-refractive-index resin materials, and the grating layer is obliquely arranged.
Preferably, the optical waveguide layer and the grating layer are made of a resin material with a refractive index of 1.71, specifically, an inclined grating is etched on the resin material, wherein the optical waveguide layer is plate-shaped, and the grating layer is positioned on the surface of the optical waveguide layer.
In fig. 1, the refractive index of the grating layer is nr (nr=1.71), the refractive index of the optical waveguide layer is n3 (n3=1.71), a represents the tilt angle, d represents the grating period, b represents the grating ridge width, h represents the grating etching depth, n1 represents the air refractive index of the incident region, ng represents the grating groove refractive index, and ng=n1=1.
The grating period of the inclined grating is 980-992 nanometers, the duty ratio is 0.74-0.76, the grating depth is 1475-1490 nanometers, and the inclination angle between the grating layer and the vertical surface is 26-27 degrees.
Preferably, the tilted grating has a grating period of 986 nm, a duty cycle of 0.75, a grating depth of 1482 nm, and a tilt angle of 26.5 °.
With the grating structure shown in fig. 1, the incident light is perpendicularly incident from the air at a center wavelength of 620 nm. Wherein the 0 and-1 orders are diffracted out of the grating structure and the-2 order diffracted light is totally internally emitted within the optical waveguide layer, as shown in fig. 2. The diffraction efficiency of the center 620 nanometer wavelength of the-2-order diffraction grating under the condition of vertical incidence of TE polarized light is calculated by adopting a strict coupled wave theory.
As shown in table 1, d is a grating period, a is an inclination angle, b is a grating ridge width, h is a grating depth, λ is an incident wavelength, and η is a-2 diffraction efficiency of TE polarized light. In the process of manufacturing the-2-level high refractive index inclined grating with the center wavelength of 620 nanometer wave band, as shown in table 1, when the grating period is 980-992 nanometers, the duty ratio is 0.74-0.76, the grating depth is 1475-1490 nanometers, and the inclination angle is 26-27 degrees. When TE polarized light is vertically incident, the-2 diffraction efficiency of the 620 nanometer wave band of the center wavelength can be basically higher than 80 percent. As can be seen from fig. 3, when the incidence angle is in the range of-0.5 ° to 2 °, the-2-order diffraction efficiency is 80% or more.
Table 1 TE diffraction efficiency of polarized light at normal incidence.
When TE polarized light is vertically incident, the grating period of the inclined grating is 986 nanometers, the duty ratio is 0.75, the grating depth is 1482 nanometers, the inclination angle is 26.5 degrees, the diffraction efficiency of the central wavelength 620 nanometers-2 orders is higher than 85 percent, and the total internal reflection is realized on the optical waveguide layer.
Example 2
This example provides the use of the high refractive index material-based-2-order tilted grating of example 1 in a near-eye display device. By using the direct writing process and the etching process, the inclined grating suitable for the AR/VR technology can be obtained, and the method has important practical prospect. The invention has the advantages of flexible and convenient use, higher diffraction efficiency and the like, and is an ideal diffraction optical element.
As described above, the present invention can be better realized, and the above-described embodiments are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention; all equivalent changes and modifications are intended to be covered by the scope of the appended claims.
Claims (3)
1. The-2-level inclined grating based on the high-refractive-index material is characterized by comprising an optical waveguide layer and a grating layer, wherein the optical waveguide layer and the grating layer are made of resin materials with refractive index of 1.71, and the grating layer is obliquely arranged;
the grating period of the inclined grating is 980-992 nanometers, the duty ratio is 0.74-0.76, the grating depth is 1475-1490 nanometers, and the inclination angle is 26-27 degrees;
etching the inclined grating on the resin material by using a direct writing process and an etching process, wherein the optical waveguide layer is plate-shaped, and the grating layer is positioned on the surface of the optical waveguide layer;
the tilted grating achieves a center wavelength of 620 nm-2 diffraction order efficiency higher than 80% and total internal reflection at the optical waveguide layer when TE polarized light is perpendicularly incident.
2. The high refractive index material based-2-order tilted grating of claim 1, wherein the tilted grating has a grating period of 986 nm, a duty cycle of 0.75, a grating depth of 1482 nm, and a tilt angle of 26.5 °.
3. Use of a high refractive index material based-2 order tilted grating as defined in any of claims 1-2 in a near-eye display device.
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| CN202210709648.0A CN115097558B (en) | 2022-06-22 | 2022-06-22 | 2-level inclined grating based on high refractive index material and application thereof |
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| CN106842397A (en) * | 2017-01-05 | 2017-06-13 | 苏州苏大维格光电科技股份有限公司 | A kind of resin holographical wave guide eyeglass and preparation method thereof and three-dimensional display apparatus |
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| CN106842397A (en) * | 2017-01-05 | 2017-06-13 | 苏州苏大维格光电科技股份有限公司 | A kind of resin holographical wave guide eyeglass and preparation method thereof and three-dimensional display apparatus |
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